To understand and ultimately prevent injury and behavioural health outcomes associated with masculinity, we assessed the influence of masculine discrepancy stress (stress that occurs when men perceive themselves as falling short of the traditional gender norms) on the propensity to engage in stereotypically masculine behaviours (eg, substance use, risk taking and violence) as a means of demonstrating masculinity. Six-hundred men from the USA were recruited via Amazon's Mechanical Turk (MTurk) online data collection site to complete surveys assessing self-perceptions of gender role discrepancy and consequent discrepancy stress, substance use/abuse, driving while intoxicated (DWI) and violent assaults. Negative binomial regression analyses indicated significant interactive effects wherein men high on gender role discrepancy and attendant discrepancy stress reported significantly more assaults with a weapon (B=1.01; SE=0.63; IRR=2.74; p=0.05) and assaults causing injury (B=1.01; SE=0.51; IRR=2.74; p<0.05). There was no association of discrepancy stress to substance abuse, but there was a protective effect of gender role discrepancy for DWI among men low on discrepancy stress (B=−1.19, SE=0.48; IRR=0.30; p=0.01). These findings suggest that gender role discrepancy and associated discrepancy stress, in particular, represent important injury risk factors and that prevention of discrepancy stress may prevent acts of violence with the greatest consequences and costs to the victim, offender and society.